Mycoplasma complicated chronic respiratory disease (CRD)

Occurrence: Worldwide.
Species affected: All.
Age affected: All.
Causes: Mycoplasma gallisepticum, M. synoviae, M. buteonis, M. meleagridis, M. iners, or Infectious bronchitis virus (IBV) and/or E. coli, and/or Newcastle disease virus and/or Infectious laryngotracheitis (ILT). Spread through egg and contact with infected litter, feed or water. Aerosaol spread also occurs. Severe ND, IBV or ILT reactions may occur after vaccination, especially if given by spray to chicks previously infected with mycoplasma or E. coli.
Effects: Signs include cough, tail bobbing when breathing, emaciation, rales, sneezes, open mouthed breathing, poor growth, decreased feed consumption, lowered egg production and poor shell quality.

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Causes

All species of bird of all ages are susceptible to chronic Mycoplasma infection. A number of different agents are involved in the aetiology of this disease. These include M. synoviae (MS) or M. gallisepticum (MG) in chickens, M. meleagridis (MM) and M. iowae (MI) in turkeys. M. synoviae (MS) is usually less pathogenic. Synergistic effects with E. coli and/or NDV and/or IBV vaccine viruses may occur. ILT can also be involved.

Mode of transmission

It is spread through eggs and contact with infected litter, feed or water. It is also transmitted by people, vehicles etc. E. coli is a secondary invader of mycoplasma-infected birds. Aerosol spread occurs. Severe ND, IBV or ILT reactions may occur after vaccination, especially if given by spray to chicks previously infected with mycoplasma or E. coli.

Clinical signs

Signs include coughing, tail bobbing when breathing, emaciation, rales, and sneezing, open mouth breathing, poor growth, decreased feed consumption, lowered egg production and shell quality.

Postmortem lesions

Yellow fibrin on the heart, liver and viscera organs, caseous air sacs, mucus in trachea and green livers can be seen.

Diagnosis

Laboratory isolation and identification of E. coli or mycoplasma from lesions. Detection of mycoplasma colonies using fluorescent antibody test, PCR, and antigen capture ELISA.

Prevention & treatment

Live and killed vaccines against MG, MS, IBV, NDV, ILTV, E. coli. exist for pullets. Depopulation of MG and MS breeder flocks. Do not use multiage breeder flocks.  Antibiotics are effective.

Special note

E. coli is a normal contaminant of the intestine, but is a primary pathogen in the respiratory tract. Birds compromised by immunosuppression due to an early infection with IBD or CAV commonly develop CRD. It is a major cause of condemnation in the processing plant.